vectors            13 trap.c         extern uint vectors[];  // in vectors.S: array of 256 entry pointers
vectors            23 trap.c             SETGATE(idt[i], 0, SEG_KCODE<<3, vectors[i], 0);
vectors            24 trap.c           SETGATE(idt[T_SYSCALL], 1, SEG_KCODE<<3, vectors[T_SYSCALL], DPL_USER);